This invention relates to an immunopotentiator comprising abrin as an active ingredient.
Abrin used in this invention is a lectin isolated from the seeds of jequirity (Abrus precatorius) which is a plant of the family Leguminosae occurring naturally in the tropical and subtropical zones. It is a kind of glycoprotein having a molecular weight of about 65,000.
Immune protection in vertebrates is known to be provided by two basic immune response systems against infections and tumor cells. One is the cellular immune response system effective mainly against infections by fungi, viruses, intracellular parasitic bacteria, etc. and against tumor cells, and the other is the humoral immune response system effective for defence mainly against infections by viruses and extra-cellular parasitic bacteria.
A substance which when injected into a living organism together with an antigen, increases the aforesaid immune responses to the antigen is known as an immuno-adjuvant [Davis, B. D. et al., Microbiology, Harper & Row Publishers, page 458, (1967)]. Heretofore, the Freund's complete adjuvant has been used mainly as the immuno-adjuvant. Since, however, the Freund's complete adjuvant is composed of killed Mycobacteria, a surface-active agent and a mineral oil, a complex operation is required for formulating it into a dosage form by mixing it with an antigen in the form of an aqueous solution, a suspension, etc., and moreover, strong necrosis or swelling occurs at the injected site. Accordingly, the Freund's complete adjuvant has been unable to be used in humans.